Q1.
(a)
A single-phase transformer has primary and secondary windings on each limb of the core. The cross-section of the magnetic core is 12 \text cm2 and the length of the magnetic path is 50 cm. The core has a relative permeability of 20000. The primary and secondary windings have 500 and 1000 turns, respectively.
(i) If the primary winding is supplied with a current of 10 A, while the secondary winding is open-circuited, calculate the self-inductance L11 of the primary winding and the mutual inductance L12 between the two coils.
(ii) If the primary winding is de-energized, while the secondary winding is connected to a source from which it draws 8 A, calculate the self-inductance L22 of the secondary winding and the mutual inductance L21 between the two coils.
(b) Draw the V-curve of a salient pole synchronous motor operating at no-load. What do you mean by normal excitation ? Explain physically why the motor operates at leading power factor under over-excitation.